Crystal tree



FIG. 1 is a Perspective view of a crystal tree showing my new design;

FIG. 2 is a Front view thereof;

FIG. 3 is a Back view thereof;

FIG. 4 is a Right-side view thereof;

FIG. 5 is a Left-side view thereof;

FIG. 6 is a Top view thereof; and,

FIG. 7 is a Bottom view thereof.

The broken lines shown in the drawings represent portions of the crystal tree that form no part of the claimed design. 

CLAIM The ornamental design for a crystal tree, as shown and described. 